C4L Specifications

Raw pre-production body in white shells – with no VIN stamp – were delivered to Jurgen Barth in Weissach where the race department would complete their production by hand. All 22 cars shared the same components with common use of left over parts. Although the most notable shared components are with the 953 and 964 Carrera 4, the car shared 763 individual part numbers sourced from no less than 15 Porsche models representing many multiples of that number in parts/part assemblies.

Upon receipt of the donor shells in Weissach the bodies were custom tabbed and seam welded for torsional stiffness to be fitted to completion by the motorsports group. Fitted were aluminum doors and front boot from the Carerra Cup car and the Makrolon engine lid with fixed rear spoiler and Makrolon sliding side windows from the 953. Remaining windows were all standard glass except for the lightened rear glass and all underbody sound deadening material and cosmoline were omitted.

Lights and fog lights were as standard and side view mirrors were Carrera Cup. What appears as an homage to the 1972 911, but resumed here for practical purposes, the right rear quarter panel featured a lidded side filler door for the oil tank mounted forward of the right rear axle. The wiring harness was custom built and an electrical cut off is mounted to the cowl supplementing the front boot and cockpit.

The donor engine type M64/01 was taken from the ROW 1989 C4 a flat six cylinder 3,600cc boxer rated at 250hp. The engine was polished and ported and fitted with custom headers (omitting heat exchangers) and an ‘open’ straight muffler increasing output to an estimated 265HP similar to the Carrera Cup car. The single pipe exhaust manifold for each row of cylinders was made of stainless steel as were the exhaust cans. The standard ECU was remapped for the free flow configuration and standard aluminum intake plenums were retained.

The transmission was lifted directly from the Paris-Dakar 953, the ancestor to the Carrera 4, incuding the front final drive, central tube, clutch and flywheel and five speed close ratio gearbox. The rear drive delivery was from the Carrera 4 and mounts were all from the Carrera Cup car.

Most unique was the manually adjustable limited slip differential allowing on-the-fly tailoring of the front-rear transfer case and lateral rear differential, torque splits. Positioned in place of the radio slot were dual round adjustment levers which hydraulically controlled these torque splits allowing for oversteer and understeer while in motion. Left wheel left to loosen and right to tighten like a threaded bolt) and right wheel to turn to the respective left/right side for bias. These manual adjustments could be manipulated to accomodate changing conditions in rally applications unlike the electronically controlled system in the 953.

Steering was manual and ABS was omitted. Most of the running gear was taken from the Carrera Cup with 5mm higher ride height. This includes stiffer and lower Carrera Cup suspension with mononballs fitted in call corners, Blisteins with stiffer progressive springs, fully adjustable anti-rollbars and an aluminum strut brace. Brakes were model 951 brake hubs, hub carriers, calipers and discs which were able to fit inside the 16” D90 alloy wheels (6J/8J) fitted with Bridgestone RE71 rubber.

Also unique were the inclusion of two brake features specifically aimed at rally applications. First, taken from the 1983 954 SC/RS, was the dual master cylinder setup with cockpit adjustable braking bias via a mechanical balance bar. The second was the hydraulic handbrake in place of the standard components. The former to balance for rear oversteer under changing weather conditions by adjustment of front to rear brake bias and the latter to induce rear over steer for off road drifting via lock up – as well as for safe parking.

The interior seems to invite racers with a stripped down interior eliminating all carpet, sound deadening material, the headliner, the rear sets and the sun visors. Creature comforts were omitted including air conditioning, heat and radio. Central locking and of course door regulators were omitted allowing for lightweight door panels with pulls. The clock was replaced by an alternator belt warning indicator and a Momo non-airbag steering wheel, a custom built lower dash with no passenger airbag and a fire extinguisher were added.

Typifying the cars split personality, other parts of the configuration seem at odds with racing such as Recaro SPG for the driver and passenger (a seat for either a passenger or a co-pilot), five point racing harnesses not six, and an aluminum bolt in Matter cage. And, while there is no provision for air jacks, there is a collapsable spare tire and manual jack, practical inclusions not suitable for racing.